PlanetCatfish.com

I've been using the Nutrafin Nitrate test kit on my tank, and quite frankly I find the colour scale chart you compare the test sample to is nothing like the colour achieved by the test. The best I can really say about them is that they are both shades of purple! (I am sure the test itself is accurate, I just don't think that the scale they want you to compare it to is in any way accurate. In fact I think it is abysmally bad.)

So, can anyone recommend a test kit that does have a properly comparable scale to compare it to?

(Why they don't just show a proper photograph of the expected results chart, I don't know. After all, they have a seemingly colour perfect photo of an angel fish and clown fish on the front of the literature!)

I agree, it is pretty much impossible to discern colour shades into exact readings, so I gave up on that a long time ago.

I now work on the very scientific principle that pale is good and dark is bad.

You can get machine that acts as spectrometer and will give you an exact reading in mg/l of the sample, but these cost a few hundred quid.

Only a few hundred? I'm almost tempted

@ Alan, the color you get is not oly dependend of the amount of nitrate, but olso of the watercolor.

If you use peat, the water can get quite yellow, and thus the reddish color from the detection mechanism will change

An apparatus such as Alan described, would measure the sample, and pure unmeasured water, in order to calculate what part of the total color comes from the nitrates, and what does not.

Nice for a laboratory, impossible to do at home